Tech Animator Dump

Friday, March 6, 2015

The scenario that I'm working with in Maya involves two referenced rigs and creating constraints and message attributes between them. Now since i'm using references in Maya, additional bones, controls or what have you may be created in either reference at any point in time. What I'm doing is creating parent constraints from one rig to the other and anytime new bones or controls are added to the on rig, I need to constrain it to the other rig with relative names automatically. This is where callbacks come into play.

Callback

After the scene is fully Open and all the references are loaded I need to check message attributes to see if one rig is "connected" to another. Here I'm using message attributes to point each rig to one another. The callback looks for this message, if found it will update the connections by creating new constraints for similarly named objects. Now I was originally using the kAfterOpen callback which should fire off after all references are loaded. It does work, but I changed to the scriptJob version, "SceneOpened", that seems to run later than the callback variant, even after viewport processing. The method being called in the callback runs and connects everything just fine. While the scene appeared to be functioning correctly, after saving and reloading the file later, all the constraints were broken and the attributes were missing. I started to panic thinking this was a new bug with saving and references. I posted on the Autodesk beta boards after trying multiple approaches to work around my problem.

The Actual Problem

I spent quite a while doing diffs on the maya ascii files. The file before the callback and the file after the callback. Here I started to notice differences in the referenceEdits. I didn't understand all the formatting so I went on a hunt for the information there. Sadly, the actual documentation that I found had no real detail in the places that I had question about. This archived Post from PosingMantis on cgsociety helped greatly. What I started to realize was that all the operations I was doing during callbacks, while still functioning in the scene afterwards, they were not saving in the referenceEdits.

Here's an example of what the connections in the refEdits look like before the callbacks. The referenced ball is parentConstrained to the referenced box.

After the callback ran, all of those reference edits were now missing, but like I said everything was still operating and working properly in the scene. This was incredibly misleading. I looked for some more documentation and I found the root of my problems.

If I was a good little tech artist I would have read ALL of the documentation on callbacks. I know what callbacks do, why would I think methods called from them wouldn't record referenceEdits. Sigh. There are specific callbacks you can run after a reference loads and you can record referenceEdits. kAfterSceneReadAndRecordEdits This one probably does precisely what I needed, the others fire off after every referenceLoads which I didn't need. However, after chatting with Brad Clark cofounder of @RigginDojo, I opted for creating a scriptNode that runs the same methods OnDemand after a "SceneOpened" scriptJob, and the scriptNode has a flag to "RecordReferenceEdits". I can also only create this in the scenes that need them.

This still may not be the best way to do it but right now it's what I needed to move forward. I hope this will be helpful to someone as none of the issues I noticed were directly obvious. Good luck!

All of our characters and animated objects have a custom scripted plugin modifier that
sits on top of the character mesh modifier stack. It stores references to the skeleton and
helper objects in the parameter blocks of the modifier. To store these object references you will see below the parameter type should probably be a #maxObjectTab type. If you are looking for something similar to
the message attributes in Maya the #maxObject parameter type, or what 3dsmax
calls weak referencing, is as close as you are going to get. Paul Neale has a
pretty good tutorial for weak referencing.

I went ahead and wrote up some functional code below to help provide a basic understanding of scripted plugin modifiers and weak referencing. If you evaluate this code a new modifier will appear in the modifier list named "AnimExportTest". It does not modify your mesh/object it is only a container for storing references and variables relative to your character.

Our version of this modifier has many more methods, attributes and options for storing animation and other references. This is more or less the core interface for evaluating incoming animatable assets to make sure they are properly setup for animation and exporting when building an animation scene, as noted in my previous post.

You may chose to build a similar interface but rather than a modifier it can be a custom shape object that lives in your scene. It's pretty much the same thing just where it lives is different.

Custom Attributes & adding Assets
When adding an asset I will merge the entire scene and inspect this custom modifier to make sure it has everything I need for animation. If it passes the validation process I will collect a list of only the objects necessary for animation and delete the remaining unnecessary objects that came into the scene. Once I have identified the valid objects I will apply a "namespace" prefix to them based on the supplied asset name. I will then stamp additional attributes onto all of the valid objects to sort them and identify them as a unique asset within the scene. You can see my post on Tech-Artists.Org for more on custom attributes. Below is an example of setting the custom asset attributes on the incoming objects.

A Bulk of the Work
Now that you have brought in a character asset into your scene in a clean and managed fashion the heavy lifting is done by your scene manager. Adding and Deleting should then become fairly trivial as your asset objects should be clearly identified. However, the swapping of your animated characters requires your tool to do much more in the way of saving animation, link constraints and export data defined in your scene. This of course relies heavily on your control rig system be it CAT, custom, or god forbid Biped +Brad Clark. Once you have a proper save and load, swapping assets should become a "breeze". I will note that 80% of my Asset Manager code is handling the saving and loading of animation. You may find many cases where you have to do a lot of code to preserve the state of your animation in relation to other objects or characters in your scene.

Feel free to ask any additional questions. I will try to follow up.
Until next time.

UPDATE: Fixed some script errors in the plugin modifier. It will now refresh the ui when you reopen it.

Saturday, September 1, 2012

Having worked on many game titles in the past its quite clear that scene building and having a way to reference or quickly update characters and rigs is very important. If you work in 3dsmax you are probably quite aware and envious of the referencing capabilities that exist in Maya. This functionality is clearly missing from 3dsmax and may likely never appear. Sure there are Xrefs but be my guest if you choose to use them and discover you don't get nearly what you need with the added benefits of instability.

So out of necessity I started work on what ultimately became our Animation Asset Manager ( AM ). The tool merges assets, Characters, Weapons, Vehicles, Props, Environments, etc. in a quick and efficient manner. Straight ahead file merging can result in a very messy file, as 3dsmax does not have native "namespace" functionality, and there may end up being a lot of object name collisions and rig linking errors. The Asset Manager handles all of these issues and bundles all of the incoming file objects into one "Asset". Now working in hugely complex scenes is quite easy as thousands of objects can now be represented as one Asset.

Adding an Asset

The artist chooses the asset type to add

Selects a file from a list of assets or locate a specific file on disk

Provide a unique name to represent the Asset

Add the number of asset instances

AssetManager - Add Character Asset

What actually happens behind the scenes is a bit more complex. The incoming file is first validated to make sure it is export ready. If the AM finds everything it needs for that asset type then it will fully merge the file. After merging, the incoming objects are checked and objects unnecessary for animation/export purposes are removed, shaders are converted to standard materials, all objects are stamped with Asset Attributes, and finally object names and layers are properly namespaced. The attributes that were added to each object were done to easily classify the objects under one "Asset". When the AM updates it scans the scene and represents each asset properly by querying the object attributes. In the past I used very light-weight user defined properties but I have converted to custom attributes as these can be properly transported between DCC apps and maintained in the FBX file format.

AssetManager - Asset Objects

Swapping an Asset - Poor Man's Referencing

As characters, weapons or props are updated the animators need to be able to easily update to the new asset when necessary. Cosmetic changes don't always mean an update needs to happen but specific rig changes may require updates. Scene callbacks are put in place to verify animated assets in files are up to date in regards to explicit external file references that are checked on scene open. The AM ensures that these objects can be swapped and any animation existing in the file is maintained, this is where a great deal of the code in this tool comes into play. This includes full character animation, IK objects, morph animation, external link constraints and any other custom animations related to the asset. We employ our own save animation functions to handle everything outside of the basic biped motion to ensure keys and motions are maintained between potentially different objects. However, making sure everything transfers properly is reliant upon making sure all animated assets are marked up properly during asset creation, another topic for another time.

Weapon Updating

Weapons are connected to our characters in a specific manner and in the past allowing animator's to do this by hand resulted in inconsistent errors and issues between DCC app and the game. The AM brings the updated weapons into the file and makes sure the weapon's are aligned and linked properly to the character. Updating the weapons is just as easy as hitting the update button when necessary. The weapon is removed from the file, the source asset file is synced in source control, and finally updated into the current animation file.

AssetManager - Update Weapons

Demonstration Video
You can watch a demonstration of the scene building and swap process below. The tool and functionality was developed and improved upon over the course of a couple projects. It was used to construct animation scenes and cinematics from our latest title Saints Row: The Third

Saturday, January 28, 2012

Animators using 3dsmax may want to use Biped as their control skeleton but for games you do not necessarily want to use this as your exported skeleton. Ryan Griffin on G+ has recently posed a question regarding building a skeleton based off of a biped. As we have done this for quite some time at Volition I felt I could offer some assistance here using Maxscript.

First we want to create a structure representing the bone data that will be used to create the skeleton. A struct in maxscript is somewhat similar to class objects that exists in other languages such as python or C#. Check out Duber's Blog for a more in depth look on maxscript structs.

struct bone_info (bone_name, parent_name, bone_xform)

Next we create a recursive function that will return the data representing each biped bone name, the parent bone name, and the bone transform. Notice that I am ignoring certain biped helper objects that don't necessarily need to become bones in our skeleton.

-- recursive function to get biped children objects
fn get_bip_children bip_obj bone_data =
(
-- make sure the current biped object has children
if (bip_obj.children != undefined) do (
-- loop through all of the current bone's children
for child in bip_obj.children do (
-- ignore these biped objects
match_footsteps = matchpattern child.name pattern:"*footsteps"
match_nubs = matchpattern child.name pattern:"*nub"
-- do not add certain objects as bones, this is a preference
if (not match_footsteps) and (not match_nubs) do (
-- create an object for the current child bone
new_bone = bone_info child.name bip_obj.name child.transform
-- update the bone_data array with the current child
append bone_data new_bone
-- see if the current child has and children
if (child.children != undefined) do (
get_bip_children child bone_data
)
)
)
)
return bone_data
)

Next up is the main function that collects the biped bone data, creates the new bones and rebuilds the hierarchy. Something that I should point out here. I am creating the actual bones using point helper objects. Almost any object in max can be used as an animatable bone and work with the Skin modifier to deform meshes. One thing to keep in mind is that I avoid creating max bones using the bone() creation method. This tends to be slow and I have found to crash Skin. You may choose to use bonesys.createbone as an alternative.

Now since we used point helpers to create the bones you may want to display these objects with links and make them look more like max bones. To do this you can go to the display panel under link display at the bottom and check both options.

The final result with a little object coloring should look like this.
There are many other things you can do once you create this skeleton such as constrain these bones directly to the biped, create additional helper bones to represent bone twists or add your own custom constraints to transform these bones any way you like.
You can download the full script here.
biped_create_skeleton.ms

Monday, October 10, 2011

I recently had to do some window handle trickery with Python and MotionBuilder. I have an external python tool that is communicating with MotionBuilder, 3dsmax, and in the near future Maya. For this post I will only be touching on the MotionBuilder implementation of the tool.
When I run the tool it will return a list of scene objects within a list view. If I select on a item in the list view it should select the object within MotionBuilder. While the selection in the scene navigator is updated, since the tool is not a child of the MotionBuilder application, MotionBuilder will not redraw the viewport. I'm quite new to MoBu but the only code I saw to potentially force redraw the scene was.

FBSystem().Scene.Evaluate()

It is likely that the Mobu viewport/rendering is on a separate thread from normal scene processing. Which would explain why the scene navigator updates and the viewport does not. The viewport only seems to update if the application is the focused application. With this in mind I decided to force change the application focus to get the results I wanted.

When the python tool makes a connection to the specific dcc app I will call the following:

This will return self.dcc_hwnd and all that really is is a window process handle or long integer. In this example it is. DCC Handle: 3214530

Now that I have stored the window handle when I select an object in my listview it will call the following:

def set_dcc_focus(self):
if self.dcc_hwnd != None:
# store the current python tool window handle
current_hwnd = win32gui.GetForegroundWindow()
# use the window handle to set focus
win32gui.SetForegroundWindow(self.dcc_hwnd)
# important to sleep here as to allow Mobu time to draw
time.sleep(0.03)
try:
# set the focus back to the python tool
win32gui.SetForegroundWindow(current_hwnd)
except:
return

With this I can click on all the objects in my external tool and see the select update 'realtime' within the MotionBuilder viewport. The code will change the window focus momentarily and just long enough to redraw the MotionBuilder viewport then immediately return focus back to the python tool. With the sleep time I have set here it is fast enough that I can be pressing down on the keyboard to step between items in the listview without noticing the app focus switching. However, I have noticed that if Motionbuilder doesn't have enough time to redraw, some things have the possibility of not rendering when the viewport is redrawn. So the sleep here could become variable and dependent on the amount of objects within the viewport.

UPDATE:
In the comments below, Kevin pointed out that you can skip all of this and modify the application.txt by adding the following line under [Timing]
NoFastIdleOnDeactivate = No